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| bio | website | |
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| age | ||
| visits | member for | 1 year, 10 months |
| seen | 2 days ago | |
| stats | profile views | 34 |
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Aug 6 |
comment |
Properties of PRNG / Hashes @Paŭlo I don't get your 'by this argument...'. A string comparison algorithm can be easily demonstrated to be O(N) with just a few small observations, whereas a 512-bit counter will simply not ever roll over to needing a second block. Only in practice, not theory, of course. :-) |
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Aug 6 |
comment |
What is the general justification for the hardness of finding preimages for cryptographic hash functions? Sure, eprint.iacr.org/2006/254 and eprint.iacr.org/2010/285 for example. What's most interesting though is how the attitudes towards SAT seems to have changed in just 4 years. From (literally) "We expect SAT solvers to find new applications as a validation and testing tool of practicing cryptanalysts" to "We found preimages for some reduced versions and showed that full function is secure against the presented attack." |
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Aug 5 |
answered | What is the general justification for the hardness of finding preimages for cryptographic hash functions? |
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Aug 5 |
comment |
How can SSL secure a two-way communication with only one key-pair? Netscape developed SSL 2.0 which is now all-but-abandoned. SSL 3.0 was developed and Netscape evaporated and handed stewardship of the protocol spec to the IETF who promptly renamed it TLS 1.0 (to fit their nomenclature). SSL 3.0 and TLS 1.0 are nearly identical. Nobody (give or take) uses TLS 1.1 or 1.2. The use of Diffie-Hellman to agree upon an ephemeral key is an option that client and server may choose to agree upon, but it's totally an option and not preferred by most sites due to the computational expense. |
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Aug 4 |
awarded | Editor |
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Aug 4 |
revised |
Reverse engineering a hash? added 414 characters in body |
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Aug 4 |
comment |
Properties of PRNG / Hashes Yeah, if you don't pay the incremental costs before the entire universe burns out, I consider it O(1). Guess I'm a coder, not a mathematician. :-) |
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Aug 3 |
answered | Is the logic for how the enigma machine worked documented somewhere? |
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Aug 3 |
awarded | Critic |
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Aug 3 |
answered | Is SHA-512 bijective when hashing a single 512-bit block? |
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Aug 3 |
answered | Reverse engineering a hash? |
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Aug 3 |
comment |
Security of N bit HMAC It might be worth restating that these security properties of HMAC rely on the attacker not having significant knowledge of the secret key, i.e., the key must represent at least 128 bits of entropy to the attacker. Sometimes you see HMAC used as an ordinary hash function with a fixed 'key' input, or the key might be something weak like a password. |
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Aug 3 |
answered | Can an Enigma-style cipher of sufficient complexity be considered secure in today's world? |
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Aug 3 |
comment |
Properties of PRNG / Hashes Well the 'input' to such a CSPRNG, the seed value, need not exceed a reasonable fixed amount. It could certainly be less than the 447 input bits consumed by a single block SHA-(n < 512) operation. Unless you want to include some ongoing reseeding policy in the length, but that's a whole 'nother discussion. :-) |
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Aug 3 |
comment |
Why does PBKDF2 xor the iterations of the hash function together? When I glanced at it the other day, it looked to me like when it was used with HMAC, the combined internal structure would allow an attacker to precompute the (k^ipad) and (k^opad) hash blocks from his dictionary, as they depend only on the password. So the attacker can save himself work proportional to (output block count + 1) over a naive implementation by the defender. This may have been an intentional design to allow the use of noniterated HMAC keying, but seems to be an undocumented consideration. |
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Aug 2 |
awarded | Teacher |
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Aug 2 |
awarded | Supporter |
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Aug 2 |
answered | Properties of PRNG / Hashes |
